U.S. patent application number 11/528461 was filed with the patent office on 2007-03-29 for wafer level image module.
This patent application is currently assigned to VISERA TECHNOLOGIES, COMPANY LTD.. Invention is credited to Hsiao-Wen Lee, Tzu-Han Lin, Pai-Chun Peter Zung.
Application Number | 20070070511 11/528461 |
Document ID | / |
Family ID | 37893544 |
Filed Date | 2007-03-29 |
United States Patent
Application |
20070070511 |
Kind Code |
A1 |
Lee; Hsiao-Wen ; et
al. |
March 29, 2007 |
Wafer level image module
Abstract
A wafer level image module includes a photo sensor for
outputting an electrical signal upon receiving light, a lens set
for focusing incident light onto the photo sensor, and an
adjustment member disposed between the photo sensor and the lens
set for controlling the distance between the photo sensor and the
lens set to compensate the focus offset of the photo sensor for
enabling the lens set to accurately focus the incident light onto
the photo sensor in an in-focus manner so as to provide a high
image quality.
Inventors: |
Lee; Hsiao-Wen; (Hsinchu
City, TW) ; Zung; Pai-Chun Peter; (Hsinchu, TW)
; Lin; Tzu-Han; (Hsinchu, TW) |
Correspondence
Address: |
BACON & THOMAS, PLLC
625 SLATERS LANE
FOURTH FLOOR
ALEXANDRIA
VA
22314
US
|
Assignee: |
VISERA TECHNOLOGIES, COMPANY
LTD.
HSIN-CHU CITY
TW
|
Family ID: |
37893544 |
Appl. No.: |
11/528461 |
Filed: |
September 28, 2006 |
Current U.S.
Class: |
359/656 ;
348/E5.028 |
Current CPC
Class: |
H01L 27/14632 20130101;
H04N 5/2257 20130101 |
Class at
Publication: |
359/656 |
International
Class: |
G02B 21/02 20060101
G02B021/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 29, 2005 |
TW |
94134100 |
Claims
1. A wafer level image module comprising: a photo sensor for
outputting an electrical signal upon receiving light; a lens set
for focusing incident light onto the photo sensor; and an
adjustment member disposed between the photo sensor and the lens
set for controlling the distance between the photo sensor and the
lens set for enabling the lens set to focus the incident light onto
the photo sensor in an in-focus manner.
2. The wafer level image module as claimed in claim 1, wherein the
lens set comprises a first transparent lens layer bonded to the
adjustment member, a second transparent lens layer, and a light
transmissive pad sandwiched between the first transparent lens
layer and the second transparent lens layer.
3. The wafer level image module as claimed in claim 1, wherein the
lens set further comprises a light transmissive pad bonded to a top
surface of the second transparent lens layer opposite to the light
transmissive pad that is sandwiched between the first transparent
lens layer and the second transparent lens layer.
4. The wafer level image module as claimed in claim 1, further
comprising a transparent spacer disposed between the photo sensor
and the adjustment member.
5. The wafer level image module as claimed in claim 4, wherein the
transparent spacer has an opening corresponding to a photo sensing
area of the photo sensor.
6. The wafer level image module as claimed in claim 1, wherein the
adjustment member comprises a glass ball spacer or a fiber
spacer.
7. The wafer level image module as claimed in claim 1, wherein said
photo sensor is a complementary metal-oxide semiconductor type
photo sensor.
8. The wafer level image module as claimed in claim 1, wherein said
adjustment member has a thickness substantially ranging 1-50
.mu.m.
9. The wafer level image module as claimed in claim 1, wherein said
adjustment member is made by means of thick film photolithography
technology.
10. A method for making a wafer level image module comprising the
steps of: a) providing a photo sensor made by an integrated circuit
manufacturing process; b) stacking a lens set made by an integrated
circuit manufacturing process on the photo sensor; c) measuring a
focus offset of said lens set and determining in-focus or
out-of-focus status of said photo sensor; and d) disposing an
adjustment member between said lens set and said photo sensor to
compensate the focus offset of said lens set so as to have said
photo sensor be in an in-focus status.
11. The method as claimed in claim 10, wherein said step (c)
comprises a sub-step of using a signal processor to check the
out-of-focus status to be a far focal or near focal status when
said photo sensor is in an out-of-focus status.
12. An apparatus for in-situ assembling and testing the wafer level
image module of claim 1, the apparatus comprising: a positioning
unit for positioning said photo sensor on said lens set and for
setting said adjustment member between said photo sensor on said
lens set; a signal pickup device electrically connected to said
photo sensor for picking up a signal from said photo sensor upon
focusing of an image onto said photo sensor by said lens set; a
signal processor electrically connected to said signal pickup
device for determining in-focus or out-of-focus status of the image
focusing on the photo sensor; and a bonding unit for bonding said
photo sensor, said adjustment member and said lens set
together.
13. The apparatus as claimed in claim 12, wherein said positioning
unit comprises a clamping device for clamping said photo sensor,
said adjustment member and said lens set together for bonding by
said bonding unit.
14. The apparatus as claimed in claim 12, wherein said positioning
unit comprises a test table for carrying said wafer level image
module and electrically connecting said wafer level image module to
said signal pickup device.
15. The apparatus as claimed in claim 12, wherein said signal
pickup device comprises a probe card electrically connected to said
photo sensor of said wafer level image module.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to image modules and more
particularly, to a wafer level image module, the method for making
the same and the apparatus for assembling and testing the same.
[0003] 2. Description of the Related Art
[0004] FIG. 12 shows a conventional CMOS (Complementary Metal-Oxide
Semiconductor) image module 80. According to this design, the CMOS
image module 80 comprises a sensor chip 82 and a lens holder 81
covering the sensor chip 82. The lens holder 81 comprises a rotary
lens barrel 83, and a lens set 84 on the center of the rotary lens
barrel 83. When the lens set 84 is mapping an image onto the sensor
chip 82, the rotary lens barrel 83 is rotatable to change the
distance between the lens set 84 and the sensor chip 82, thereby
focusing light rays on the sensor chip 82.
[0005] FIG. 13 shows an image module according to WO2004/027880.
This design of image module comprises an image pickup device 103
and a set of lenses 111 and 127. The lenses 111 and 127 are
arranged in a stack and closely attached to the image pickup device
103 to map the image of incident light rays onto the image pickup
device 103. The main feature of this patent is that the image
pickup device 103 and the lenses 111 and 127 are made through an
integrated circuit manufacturing process to minimize the size for
use in a cell phone, PDA, or any of a variety of other consumer
electronics.
[0006] However, during the fabrication of the image module
according to WO2004/027880, the lenses 111 and 127 may deform by
the manufacturing process and the manufacturing temperature. The
focal distance of the finished product shows a 0-50 .mu.g m error
when compared to the original theoretical design. In actual
practice, the lenses 111 and 127 cannot accurately focus the image
of incident light rays onto the image pickup device 103, resulting
in an out-of-focus problem (see the imaginary line A or B in FIG.
13). Further, when mounting the lenses 111 and 127 on the image
pickup device 103, the respective size tolerance, for example, 0-20
.mu.m thickness tolerance of each glass chip makes distance control
between the lenses 111 and 127 and the image pickup device 103
difficult, resulting in inaccurate focusing of the lenses 111 and
127 on the image pickup device 103.
SUMMARY OF THE INVENTION
[0007] The present invention has been accomplished under the
circumstances in view. It is an objective of the present invention
to provide a wafer level image sensor, which has adjustment means
to compensate focus offset, thereby improving the image mapping
quality.
[0008] It is another objective of the present invention to provide
a wafer level image sensor assembly apparatus, which allows in-situ
adjustment and test of each assembled wafer level image sensor,
assuring a high quality of each assembled wafer level image
sensor.
[0009] It is still another objective of the present invention to
provide a wafer level image sensor assembly method, which is
practical to assemble high quality wafer level image sensors.
[0010] To achieve these objectives of the present invention, the
wafer level image module comprises a photo sensor, a lens set, and
an adjustment member. The photo sensor outputs an electrical signal
when induced by light. The lens set maps the image of incident
light rays onto the photo sensor. The adjustment member is set
between the photo sensor and the lens set to control the distance
between the photo sensor and the lens sent, and to compensate the
focus offset of the photo sensor, enabling the lens set to
accurately focus the image of incident light rays onto the photo
sensor.
[0011] The method for making a wafer level image module comprises
the steps of a) providing a photo sensor, b) stacking a lens set on
the photo sensor, c) measuring a focus offset of the lens set, and
d) disposing an adjustment member between the lens set and the
photo sensor to compensate the focus offset of the lens set so as
to have the photo sensor be in an in-focus status.
[0012] The present invention also provides an apparatus for in-situ
assembling and testing the aforesaid wafer level image module. The
apparatus comprises a positioning unit for positioning the photo
sensor on the lens set and for setting the adjustment member
between the photo sensor on the lens set, a signal pickup device
electrically connected to the photo sensor for picking up a signal
from the photo sensor upon focusing of an image onto the photo
sensor by the lens set, a signal processor electrically connected
to the signal pickup device for determining in-focus or
out-of-focus status of the image focusing on the photo sensor, and
a bonding unit for bonding the photo sensor, the adjustment member
and the lens set together.
[0013] Further scope of applicability of the present invention will
become apparent from the detailed description given hereinafter.
However, it should be understood that the detailed description and
specific examples, while indicating preferred embodiments of the
invention, are given by way of illustration only, since various
changes and modifications within the spirit and scope of the
invention will become apparent to those skilled in the art from
this detailed description.
BRIEF DESCRIPTION OF THE DRAWING
[0014] The present invention will become more fully understood from
the detailed description given hereinbelow and the accompanying
drawings which are given by way of illustration only, and thus are
not limitative of the present invention, and wherein:
[0015] FIG. 1 is a schematic sectional view of a wafer level image
module in accordance with a first preferred embodiment of the
present invention;
[0016] FIG. 2 is a perspective view of a wafer level image module
assembly apparatus according to the present invention;
[0017] FIG. 3 is a schematic view showing the clamping device
clamped the stacked first water and the second wafer on the test
table;
[0018] FIG. 4 is a schematic side view showing the first water and
the second wafer stacked together and placed on the test table;
[0019] FIG. 5 is a schematic drawing showing an out-of-focus status
of an image mapped on the photo sensor according to the present
invention;
[0020] FIG. 6 is similar to FIG. 4, showing the adjustment member
set in between the first wafer (photo sensors) and the second wafer
(lens sets);
[0021] FIG. 7 is a schematic drawing showing an image mapped onto
the photo sensor after installation of the adjustment member in the
wafer level image module according to the present invention;
[0022] FIG. 8 is schematic drawing showing an in-focus status of an
image mapped on the photo sensor according to the present
invention;
[0023] FIG. 9 is a schematic sectional view of a wafer level image
module in accordance with a second preferred embodiment of the
present invention;
[0024] FIG. 10 is a schematic sectional view of a wafer level image
module in accordance with a third preferred embodiment of the
present invention;
[0025] FIG. 11 is a schematic sectional view of a wafer level image
module in accordance with a fourth preferred embodiment of the
present invention;
[0026] FIG. 12 is a schematic drawing showing an image module
according to the prior art, and FIG. 13 is a schematic drawing
showing another design of image module according to the prior
art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0027] As shown in FIG. 1, a wafer level image module 10 in
accordance with a first preferred embodiment of the present
invention comprises a photo sensor 20, an adjustment member 25, and
a lens set 30. The photo sensor 20 can be a CMOS (Complementary
Metal-Oxide Semiconductor) image sensor or CCD (Charge Coupled
Device) image sensor adapted to output an electrical signal when
induced by light. The photo sensor 20 is mounted on the top side
thereof with a light transmissive spacer 22. The light transmissive
spacer 22 protects the photo sensor 20 against outside pollutants
and moisture. The adjustment member 25 can be a glass ball spacer
25 or fiber spacer formed on the top surface of the transmissive
spacer 22 by sputtering deposition, spot adhesive, or screen
printing. The adjustment member 25 has a thickness about 1-50 .mu.g
m. This thickness is determined subject to the depth of focus
required and the focus offset. Further, the adjustment member 25
can be formed on the transmissive spacer by means of thick film
photolithography technology, or directly made of a glass plate.
Alternatively, the adjustment member 25 can be formed on the lens
set 30.
[0028] The lens set 30 can be molded from transparent ultraviolet
polymers, or made by etching. The lens set 30 is covered on the top
side of the adjustment member 25 such that the adjustment member 25
is sandwiched between the lens set 30 and the photo sensor 20 for
controlling the distance between the lens set 30 and the photo
sensor 20. Incident light rays go through the lens set 30 to the
photo sensor 20, thereby mapping the image onto the photo sensor
30. The focus offset in which the lens set 30 maps the image of
incident light rays onto the photo sensor 20 is about 0-50 .mu.g m.
When setting the adjustment member 25 in between the lens set 30
and the photo sensor 20, the thickness of the adjustment member 25
compensates the focus offset, thereby controlling the precision of
the focal distance of the lens set 30 within the desired depth of
focus. For an image module of FNO equal to 2.8 and pixel size 3.6
.mu.m, the focus precision is about 10 .mu.m. By means of the
adjustment member 25 to compensate light rays, incident light rays
are accurately focused on the photo sensor 20.
[0029] When making the aforesaid wafer level image module 10, an
assembly apparatus 40 is used for in-situ assembly and in-situ test
of wafer level image modules 10. The structure of this assembly
apparatus 40 is outlined hereinafter with reference to FIGS. 2
through 4.
[0030] As illustrated in FIGS. 2-4, the assembly apparatus 40
comprises a positioning unit 42, a signal pickup device 43, a
signal processor 46, and a bonding unit 48. The positioning unit 42
comprises a base 50 and a test table 51. The base 50 supports a
sliding carrier 52 and a clamping device 54. The sliding carrier 52
is movable in and out of the base 50 to carry wafer level image
modules 10. The clamping device 54 is adapted to hold wafer level
image modules 10 in position and to place wafer level image modules
10 on the test table 51. The signal pickup device 43 comprises a
probe card 44. The signal pickup device 43 is mounted in the base
50 of the positioning unit 42. The signal processor 46 is
electrically connected to the signal pickup device 43, and adapted
to check in-focus or out-of-focus status of the image signal picked
up from wafer level image modules 10. The bonding unit 48 is
adapted to bond the photo sensor 20, adjustment member 25 and lens
set 30 of wafer level image modules 10.
[0031] The assembly process of the wafer level image module 10 by
the assembly apparatus 40 includes the following steps.
[0032] Step I: Perform an integrated circuit manufacturing process
to prepare a first wafer 56. As shown in FIG. 2, the first wafer
has a plurality of photo sensors 20 each carrying a first alignment
mark (not shown).
[0033] Step II: Perform an integrated circuit manufacturing process
to prepare a second wafer 58, which has a plurality of lens sets 30
each carrying a second alignment mark (not shown).
[0034] Step III: Place the first water 56 in the sliding carrier 52
of the assembly apparatus 40 and then stack the second wafer 58 on
the first wafer 56 to have the second alignment marks of the lens
sets 30 in alignment with the first alignment marks of the photo
sensors 20 respectively, and then, as shown in FIG. 3, use the
clamping device 54 to pre-bond the first wafer 56 and the second
wafer 58 and to place the stacked first water 56 and second wafer
58 on the test table 51 to have the photo sensors 20 correspond to
the probe card 44.
[0035] Step IV: Control the test table 51 to electrically connect
the stacked first water 56 and second wafer 58 to the probe card
44, as shown in FIG. 4. The test table 50 can move the stacked
wafers 56 and 58 horizontally or tilt the stacked first water 56
and the second wafer 58 subject to test requirements.
[0036] Step V: Operate the signal processor 46 to receive
electrical signal from the signal pickup device 43 so as to obtain
the focus offset in which the respective lens sets 30 map the image
of incident light rays onto the respective photo sensors 20 for
determining in-focus or out-of-focus status of the photo sensors 20
(see FIG. 5) and discriminating far coal or near focal status in
case of out-of-focus status.
[0037] Step VI: Move the sliding carrier 52 out of the base 50, and
then apply the prepared adjustment member 25 to the first wafer 56
and the second wafer 58 to have the adjustment member 25 be
sandwiched between the lens sets 30 and the photo sensors 20, as
shown in FIG. 6, and then electrically connect the integrated wafer
level image modules of the stack of wafers 56 and 58 and adjustment
member 25 to the probe card 44.
[0038] Step VII: Repeat the aforesaid steps IV through VI if the
improved image, as shown in FIG. 7, produced by the photo sensors
20 still lightly shows an out-of-focus status till the in-focus
status shown in FIG. 8 where the adjustment member 25 accurately
compensates the focus offset.
[0039] Step VIII: Operate the clamping device 54 to hold tight the
first wafer 56 and the second wafer 58, and then operate the
bonding unit 48 to bond the first wafer 56, the adjustment member
25 and the second wafer 58 together.
[0040] Step IX: Cut the stacked wafers 56 and 58 and adjustment
member 25 into single chips, i.e., individual wafer level image
modules 10.
[0041] When the lens sets 30 of the second wafer 58 are stacked on
the photo sensors 20 of the first wafer 56 by means of the
aforesaid assembly apparatus 40 and the aforesaid assembly process,
the signal processor 46 is used to check in-focus or out-of-focus
status of the electrical signal received from the signal pickup
device through the photo sensors 20. If the photo sensors 20 are at
an out-of-focus status, the thickness of the adjustment member 25
is adjusted to correct the out-of-focus status of the photo sensors
20 to an in-focus status, assuring image quality of the assembled
wafer level image modules 10. Further, by means of changing the
thickness of the adjustment member 25, the distance between the
respective lens sets 30 and the respective photo sensors 20 is
relatively adjusted, thereby accurately compensating the focus
offset between the respective lens sets 30 and the respective photo
sensors 20 so that the respective lens sets 30 accurately focus
light rays onto the respective photo sensors 20.
[0042] As stated above, the invention uses the structure of the
adjustment member to have the wafer level image module provide a
better image quality.
[0043] FIG. 9 shows a wafer level image module 60 in accordance
with a second embodiment of the present invention. Similar to the
aforesaid first embodiment of the present invention, the wafer
level image module 60 comprises a photo sensor 61, a lens set 62,
and an adjustment member 63 sandwiched between the photo sensor 60
and the lens set 62. The main feature of this second embodiment is
that the lens set 62 comprises a first lens layer 64, a second lens
layer 65, a first transmissive pad 66 sandwiched between the first
lens layer 64 and the second lens layer 65, and a second
transmissive pad 67 bonded to the top surface of the second lens
layer 65 opposite to the first transmissive pad 66. The first lens
layer 64 is bonded to the adjustment member 63 above the photo
sensor 61. The first lens layer 64 and the second lens layer 65 are
transparent for mapping the image of incident light rays onto the
photo sensor 61. This lens set 62 enables the wafer level image
module 60 to have more image characteristics.
[0044] FIG. 10 shows a wafer level image module 70 in accordance
with a third embodiment of the present invention. This third
embodiment is substantially similar to the aforesaid second
embodiment with the exception that the transmissive spacer 72 on
the photo sensor 71 has an opening 73 corresponding to the photo
sensing area of the photo sensor 71. This third embodiment achieves
the same various effects as the aforesaid first and second
embodiments of the present invention.
[0045] FIG. 11 shows a wafer level image module 75 in accordance
with a fourth embodiment of the present invention. According to
this fourth embodiment, the adjustment member 76 is directly bonded
to the surface of the photo sensor 77, and the first lens layer 79
of the lens set 78 is bonded to the adjustment member 76. This
fourth embodiment achieves the same various effects as the
aforesaid various embodiments of the present invention.
[0046] The invention being thus described, it will be obvious that
the same may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the invention,
and all such modifications as would be obvious to one skilled in
the art are intended to be included within the scope of the
following claims.
* * * * *